Re: [PATCH v1A 1/2] x86/fred: Fix build with clang

Borislav Petkov
2024-01-30T10:35:11Z

On Sun, Jan 28, 2024 at 10:45:21PM -0800, Xin Li wrote:
> Remove the .fill statement that referneces asm_fred_entrypoint_kernel()
> before it's defined, which breaks clang build.
>
> Use the .org directive instead to fill "int3" into the memory between
> asm_fred_entrypoint_user() and asm_fred_entrypoint_kernel().
>
> Fixes: 5e0636a41485 ("x86/fred: FRED entry/exit and dispatch code")
> Reported-by: Borislav Petkov (AMD) <bp@alien8.de>
> Link: https://lore.kernel.org/lkml/20240126100050.GAZbOC0g3Rlr6otZcT@fat_crate.local/
> Signed-off-by: Xin Li <xin3.li@intel.com>
> ---
>
> Change since v1:
> * Use ".org ..., 0xcc" to fill "int3" into memory (H. Peter Anvin).
> ---
> arch/x86/entry/entry_64_fred.S | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S
> index eedf98de7538..a02bc6f3d2e6 100644
> --- a/arch/x86/entry/entry_64_fred.S
> +++ b/arch/x86/entry/entry_64_fred.S
> @@ -43,14 +43,12 @@ SYM_INNER_LABEL(asm_fred_exit_user, SYM_L_GLOBAL)
> _ASM_EXTABLE_TYPE(1b, asm_fred_entrypoint_user, EX_TYPE_ERETU)
> SYM_CODE_END(asm_fred_entrypoint_user)
>
> -.fill asm_fred_entrypoint_kernel - ., 1, 0xcc
> -
> /*
> * The new RIP value that FRED event delivery establishes is
> * (IA32_FRED_CONFIG & ~FFFH) + 256 for events that occur in
> * ring 0, i.e., asm_fred_entrypoint_user + 256.
> */
> - .org asm_fred_entrypoint_user + 256
> + .org asm_fred_entrypoint_user + 256, 0xcc
> SYM_CODE_START_NOALIGN(asm_fred_entrypoint_kernel)
> FRED_ENTER
> call fred_entry_from_kernel
> --

Considering how we're still very early in the game, I'm going to fold
those into the respective patches and rebase so that we have as clean
a branch as possible.

Thx.

--
Regards/Gruss,
Boris.